Scanning apparatuses are widely used for scanning images of paper documents. Consequently, the contents of the paper documents can be converted into electronic files. The electronic files may be further spread, managed or stored by the user. With the maturity of scanning technologies, the scanning apparatuses have experienced great growth and are now rapidly gaining in popularity. In the early stage, the scanning apparatus can only scan one side of the document. For scanning both sides of the document, after one side of the document has been scanned, the document should be manually turned over so as to scan the other side of the document. However, the process of manually turning over the document is troublesome. For solving the drawbacks, a duplex scanning apparatus has been developed to scan both sides of the document.
FIG. 1 is a schematic side view illustrating a conventional duplex scanning apparatus. As shown in FIG. 1, the conventional duplex scanning apparatus 1 comprises a sheet entrance 10, a sheet exit 11, a sheet feeding channel 12, a sheet transfer channel 13, an inverting channel 14, an image reading module 15, a transfer roller assembly 16, a sheet input tray 17, a sheet output tray 18, and a sheet pick-up module 19. The sheet feeding channel 12 is arranged between the sheet entrance 10 and the sheet transfer channel 13. The sheet transfer channel 13 is arranged between the sheet feeding channel 12 and the sheet exit 11. A first end D11 of the inverting channel 14 is connected to the junction between the sheet feeding channel 12 and the sheet transfer channel 13. A second end D12 of the inverting channel 14 is connected to the sheet transfer channel 13. The image reading module 15 is located in the sheet transfer channel 13 for reading the image of a document. The transfer roller assembly 16 comprises plural transfer rollers 161˜163 for transferring the document that is located within the sheet feeding channel 12, the sheet transfer channel 13 and the inverting channel 14. Moreover, the sheet input tray 17 is located near the sheet entrance 10. The documents to be scanned are placed on the sheet input tray 17, and sequentially fed into the sheet feeding channel 12 by the sheet pick-up module 19. The sheet output tray 18 is located near the sheet exit 11 for supporting the document that is ejected from the sheet exit 11.
Moreover, the conventional duplex scanning apparatus 1 further comprises a first sheet sensing module 81, a second sheet sensing module 82, and a controller 83. The sheet pick-up module 19, the first sheet sensing module 81 and the second sheet sensing module 82 are all electrically connected to the controller 83. The first sheet sensing module 81 is located near the first end D11 of the inverting channel 14. That is, the distance between the first sheet sensing module 81 and the first end D11 of the inverting channel 14 is smaller than the distance between the first sheet sensing module 81 and the second end D12 of the inverting channel 14. Moreover, the first sheet sensing module 81 is used for sensing the transmitting status of the document in the inverting channel 14. When a front edge or a rear edge of the document is transferred through the first sheet sensing module 81, the first sheet sensing module 81 issues a first sensing signal to the controller 83. The second sheet sensing module 82 is located near the sheet entrance 10 for sensing the transmitting status of the document in the sheet feeding channel 12. When the front edge or the rear edge of the document is transferred through the second sheet sensing module 82, the second sheet sensing module 82 issues a second sensing signal to the controller 83.
The operations of the conventional duplex scanning apparatus 1 will be illustrated by referring to the sheet transfer paths S11˜S16 of FIG. 1. Furthermore, the duplex scanning apparatus 1 may be operated in a single-sided scanning mode or a duplex scanning mode. Hereinafter, the operations of the conventional duplex scanning apparatus 1 in the single-sided scanning mode will be illustrated in more details. Firstly, a document P11 is fed into the sheet feeding channel 12 through the sheet entrance 10 by the sheet pick-up module 19. Then, the document P11 is transmitted from the sheet feeding channel 12 to the sheet transfer channel 13, so that the image of the first side P11A of the document P11 is read by the image reading module 15. After the reading operation is performed by the image reading module 15, the document P11 is transmitted to the sheet exit 11 and ejected to the sheet output tray 18. Meanwhile, the single-sided scanning operation on the document P11 is completed.
Furthermore, when the document P11 is introduced into the sheet feeding channel 12 and the front edge or the rear end of the document P11 is transferred through the second sheet sensing module 82, the second sheet sensing module 82 issues a second sensing signal to the controller 83. In response to the second sensing signal, the controller 83 will drive the sheet pick-up module 19 to feed a next document P12 into the sheet feeding channel 12. Subsequently, the next document P12 is transmitted and scanned by the similar process of transmitting and scanning the document P11, and thus the single-sided scanning operation on the next document P12 is completed.
The conventional duplex scanning apparatus 1 in the duplex scanning mode may be implemented by two operating approaches. Hereinafter, a first operating approach of the duplex scanning mode will be illustrated in more details. After the conventional duplex scanning apparatus 1 is operated in the duplex scanning mode and the duplex scanning apparatus 1 is activated, the document P11 is fed into the sheet feeding channel 12 through the sheet entrance 10. Then, the document P11 is transmitted from the sheet feeding channel 12 to the sheet transfer channel 13, so that the image of the first side P11A of the document P11 is read by the image reading module 15. After the reading operation is performed by the image reading module 15, the document P11 is transmitted to the second end D12 of the inverting channel 14. Then, the document P11 is introduced to the inverting channel 14. Then, the document P11 is introduced into the sheet transfer channel 13 again, and thus the image of the second side P11B of the document P11 is read by the image reading module 15.
Moreover, the plural scanned documents which are outputted from the sheet exit 11 and placed on the sheet output tray 18 should be in the same order as the original stack of documents on the sheet input tray 17. For achieving the purpose, after the image of the second side P11B of the document P11 is read by the image reading module 15, the document P11 is transmitted to the second end D12 of the inverting channel 14 again. Then, the document P11 is introduced to the inverting channel 14 again. After the document P11 is introduced into the sheet transfer channel 13 again, the document P11 is transmitted to the sheet exit 11 and ejected to the sheet output tray 18. Meanwhile, the duplex scanning operation on the document P11 is completed.
Furthermore, when the document P11 is transmitted to the sheet exit 11 and ejected to the sheet output tray 18, the controller 83 will drive the sheet pick-up module 19 to feed the next document P12 into the sheet feeding channel 12. Subsequently, the next document P12 is transmitted and scanned by the similar process of transmitting and scanning the document P11, and thus the duplex scanning operation on the next document P12 is completed.
A second operating approach of the duplex scanning mode will be illustrated as follows. When the document P11 is introduced to the inverting channel 14 and the front edge or the rear end of the document P11 is transferred through the first sheet sensing module 81 at the last time, the first sheet sensing module 81 issues a first sensing signal to the controller 83. In response to the first sensing signal, the controller 83 will drive the sheet pick-up module 19 to feed the next document P12 into the sheet feeding channel 12. Subsequently, the next document P12 is transmitted and scanned by the similar process of transmitting and scanning the document P11, and thus the duplex scanning operation on the next document P12 is completed.
In the modern society, it is necessary to further reduce the time period of performing the duplex scanning operation on the document by the duplex scanning apparatus in order to enhance the working efficiency.